The present invention relates to a data printing device used in a camera to print data such as date and/or time on a frame of a roll film.
A conventional data printing device includes a light emitting device and an imaging optical system. The light emitting device includes a plurality of LEDs (light emitting diodes) aligned along a line perpendicular to a winding direction of a roll film and the imaging optical system forms light points corresponding to the LEDs on the film. The LEDs are controlled in synchronism with winding of the roll film to print data, such as a date, as a dot matrix image.
In the conventional data printing device, the LEDs are independently fixed to a circuit board and, thus, a distance between adjacent LEDs must be relatively large due to the size of the packages of the LEDs. For example, the distance between light emitting points of adjacent LEDs is generally more than 0.5 mm. accordingly a distance between the light emitting points at the ends of a series of seven LEDs is at least 3.3 mm where the device includes seven LEDs.
On the other hand, the size of characters (letters) of the printed data should be limited within a range of about 0.4-0.7 mm in a direction perpendicular to the winding direction so that the printed data do not interfere with a picture on a developed photograph. Thus, the imaging optical system of the conventional device is a reducing optical system for which an imaging magnification is arranged within a range of about 0.1-0.2 times.
A problem arises in that the printing position on the film may vary depending on errors, such as a positioning error or a manufacturing error, relating to the imaging optical system. Further, the displacement of the printing position due to a given error increases as the magnification decreases. Thus, the error tolerance of a conventional device is low. Therefore, the imaging optical system of the conventional data printing device must be manufactured and positioned with higher accuracy in order to ensure a constant printing position; however, such measures increase the cost of assembling and manufacturing.
Particularly, since many parts of recent cameras are made from plastics, errors in the positioning of the imaging optical system are largely affected by shape errors generated during molding or deformations due to variations of temperature of the plastic parts.